A set of data lists ratios r-/r+ for perfect packing in structures having coordination numbers of four, six, and eight. In practice a range of values for these ratios is observed within a series of compounds having the same structure. The typical range for the three coordination numbers are (4.44 - 2.44) for coordination number four; (2.44 - 1.37) for coordination number six; 1.37 and below for coordination number eight. With this in mind, predict coordination numbers of four, six, or eight for the compounds NaF, KBr and LiCl